1. Field of the Invention
The present invention relates to a V-type engine which is transversely mounted in an engine compartment formed at an end of a vehicle body.
2. Description of the Related Art
In many passenger vehicles (or vehicles), an engine is mounted in an engine compartment provided at the front end of a vehicle body adjacent to a cabin.
A multiple cylinder engine is long if it is a straight in-line cylinder engine, and hence in recent years, an increasing number of multiple cylinder engines have been constructed such that a V-type engine in which cylinders are divided into right and left banks is transversely mounted in an engine compartment.
To protect occupants from an impact in the event of a collision, passenger vehicles are required to ensure safety against the collision. Accordingly, an engine compartment is usually set as a crushable zone, and when an impact equal to or greater than a predetermined value is applied via the front end of a vehicle body, a frame of the vehicle body, which forms the engine compartment, is crushed to absorb an impact energy and protect a cabin where occupants are seated.
However, the engine is not crushed in the event of a vehicle collision since it is rigid. Thus, in the event of a vehicle collision, the engine compartment is crushed from the front end thereof, and the crushed part of the engine compartment abuts an engine block, and when an impact is input to the engine block, the engine block is displaced rearward while crushing the frame of the engine compartment, and abuts a toe board which partitions the vehicle body into the cabin and the engine compartment, and then causes e.g., deformation of the toe board, so that the impact can be absorbed.
Particularly in the case of the V-type engine, since it is transversely mounted in the engine compartment, large-sized engine accessory (such as a compressor for an air conditioner, an oil pump for power steering, and an alternator) is disposed at a location which is substantially level with a bumper to which impact is input, and the bank in the rear is likely to abut the toe board first.
The safety of vehicles against collision has been climbing to a higher level year by year.
The engine compartment, however, is restricted by the design of a vehicle, a car model, and so forth, and hence it is difficult to secure a large space required for a high collision safety. Particularly in the transverse-mounted V-type engine, both banks are protruded in the direction of the length of a vehicle, and hence it is difficult to secure a sufficient crushable zone.
Therefore, regarding the V-type engine, the technology in which the axes of cylinders are offset from the center of a crankshaft has been proposed. According to this technology, the axes of cylinders in respective banks are offset from the center of the crankshaft in the rotational direction of the crankshaft, and the banks are drawn along the axes of the cylinders to the center of the crankshaft, so that the distance between the center of the crankshaft and the lower surfaces of the cylinders in the banks (i.e., the level of the cylinder surface) can be reduced to make the V-type engine compact (refer to Japanese Laid-Open Patent Publication No. 3-281901, for example)
However, if the banks are drawn along the axes of the cylinders to the center of the crankshaft, it is necessary to modify many parts of an engine. Moreover, if the banks are drawn to the center of the crankshaft, the lower surfaces of the cylinders in one bank may enter into the cylinders in the other bank and interfere with connecting rods of the bank, and some measures must be taken to address this problem.
For this reason, the above technology has the problem that the V-type engine is considerably complicated in structure and requires high cost.